Progressive forging of multi-throw crankshafts



April 21, 1964 H. ROBRA ETAL 3,129,488

PROGRESSIVE FORGING OF MULTI-THROW CRANK-SHAFTS Filed May 4, 1961 4 Sheets-Sheet 1 J 7 I mmvron 1 /9/01? AET Apr 1964 H. ROBRA ETAL PROGRESSIVE FORGING OF MULTI-THROW CRANK-SHAFTS 4 Sheets-Sheet 2 Filed May 4, 1961 III.

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A ril 21, 1964 H. ROBRA ETAL 3,129,488

PROGRESSIVE FORGING OF MULTI-THROW CRANK-SHAFTS Filed May 4, 1961 4 Sheets-Sheet 5 INVEN TOR.

April 21, 1964 H. ROBRA ETAL 3,129,488

PROGRESSIVE FORGING OF MULTI-THROW CRANK-SHAFTS Filed May 4, 1961 4 Sheets-Sheet 4 ET 'I- & m Q mw- '1 v8 INVENTORS 19 54/1411?- 2081?? /6424 Ha/vz Jen/5K:

BY 44% AM WM ATTORNEY United States Patent 3,129,488 PROGRESSIVE FORGING 0F MULTI-THROW CRANKSHAFTS Heirnut Rohra, Mulheim (Rain), and Karl Heinz Deneke,

Bochum, Germany, assignors to Schloernann Aktlengeseilschaft, Dusseldorf, Germany Filed May 4, 1961, Ser. No. 107,853 Claims priority, application Germany May 20, 1960 1 (Iiairn. (Cl. 29-6) This invention relates to a method for the progressive forging of multi-throw crank-shafts from a blank, particularly a round blank, with pressed-in bearlng or ournal portions, wherein each thickening between two clamped bearing positions is pressed flat over the length of the crank-pin to be producul, to about the thickness thereof, while the crank-webs are pre-pressed laterally, whereupon, with lateral enclosing of the crank-webs, the crank-pin part is taken up on its parallel faces, driven home on to a supporting abutment, and then pressed down into approximately crank-pin form, with displacement of material into the crank-webs. This method is covered by German Patent No. 957,007, British Patent No. 777,151, United States Patent No. 2,891,299, and French Patent No. 1,121,589.

Starting from a rough-forged round bar, the said method is therefore composed of three main operations;

Operation 1: Pressing the shaft bearings into the round bar at the correct distance between the centre lines of the bearings;

Operation 2: Pressing fiat the pressed-in thickenings at the correct radial positions of the crank-webs;

Operation 3: Driving home and pressing out the crankwebs and the crank-pins.

This third operation is subdivided into three stages, for during the first portion of the stroke of the punch or ram there is a shifting of the flattened thickening out of the centre line of the shaft until the thickening engages the supporting abutment, which is suitably profiled. There follows, as the second operation, the filling of the lower die or swage chamber, the material then bearing completely on and conforming to the profiled abutment. Finally, after the filling, the punch penetrates further into the thickening and displaces material therefrom into the crank-webs, during which a rise of material takes place along the punch.

It is accordingly the principal object of this invention to provide a method of progressively forging a crankshaft from a round shaft blank having spaced journals and an enlarged portion therebetween, which method serves to eliminate the wrinkles formed in the metal at the point of juncture between the enlarged portion and the journals resulting from the prior method of forging a crankshaft, thereby preventing weakening of the crankshaft at these points.

Further objects and advantages of the invention will be apparent from the following description taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a sectional view showing a known apparatus for forging a crankshaft from a blank having a thickened portion between spaced bearing or journal portions;

FIG. 2 is a sectional view taken substantially on the line 11-11 of FIG. 1;

FIG. 3 is a sectional view similar to FIG. 1, and showing a subsequent known step in the operation of forging a crankshaft;

FIG. 4 is a sectional view taken substantially on the line IV-IV of FIG. 3;

FIG. 5 is a sectional view similar to FIG. 3, but showing a further step in the conventional forging operation 3,129,488 Ice Patented Apr. 21, 1964 and also showing the completed crankshaft resulting from the conventional forging operation;

FIG. 6 is a sectional View taken substantially on the line VI-VI of FIG. 5;

FIG. 7 is a sectional view showing the blank and clamping means prior to the first step of the method of this invention, and showing the resulting form of the blank after the first step;

FIG. 8 is a sectional View on the line VIII-VIII of FIG. 10, and showing the apparatus utilized in a further step of this invention;

FIG. 9 is a sectional view similar to FIG. 8, and showing the crankshaft after completion of this step of the invention;

FIG. 10 is a top plan view with parts in section taken substantially on the line XX of FIG. 8, and showing the relationship of the parts of the apparatus and the partially formed blank; and,

FIG. 11 is a sectional View similar to FIG. 5, the final step of the method of this invention together with the completed crankshaft resulting therefrom.

By 1 are denoted the lower halves of holding bearings 1, 2, which hold the aforementioned rough forged round bar or blank, which has been provided with thickenings 3 and shaft bearings or axle journals 4, pressed in during the forging of the blank. The thickening 3 is pressed fiat in operation 2 as set forth above, wherein it is flattened, as far as the surface 5, to the length of the crank-pin to be produced, while the adjacent portions 6, from which the crank-webs are to be formed, are flattened only as far as the surface 6a (FIGURES 1 and 2). In the manner mentioned by the said prior Patent No. 2,891,299 there is provided, between the lower holding bearings 1, a profiled supporting abutment 7, which is shaped as a reproduction of the shape to be imparted to the crankpin and the ends of the crank-webs. Moreover a forked punch or ram 8 is provided, the prongs or tines 8b of which can travel downwards, in the region of the flattening 5, on both sides of the thickening, and in so doing hold the thickening in the region of the surfaces 5 lateral- 1y, while the surface 8a of the punch shifts the thickening downwards. Hence the upper boundary line 35b of the thickening at first assumes approximately the form So, while the lower boundary line 9 of the thickening passes into about the form 9a. The thickening is th fore shifted downwards b showing erey about the amount a, as it comes into contact with the profiled abutment 7. FIG- URES 3 and 4 show the forging operation when the punch 8 has descended a little further, so that the under side of the thickening already begins to adapt itself to the abutment 7. When the punch 8 has travelled still further downwards, as indicated in FIGURES 5 and 6, the crank-pin 10 is formed, while material is displaced upwards into the cranlewebs, in the direction of the arrows 11.

Now it has been found that with this method of working, particularly when short bearings are desired on the shaft, wrinkles are formed at the positions x, indicated in FIGURE 5; for with the displacement downwards of the flattened thickening, represented in FIGURE 3, the point y is also shifted a 'short distance downwards. Upon the subsequent filling or" the die, represented as in FIG- URES 3 and 4, and pressing-out of the crank-pin, as in FIGURES 5 and 6, the cavity occurring at the point y does indeed more or less disappear (point x in FIGURE 5), but the material at this position wrinkles and does not reach its desired full strength.

The object of this invention, therefore, is to prevent this wrinkling. This aim is attained by interposing an operation 1a between the operations hereinbefore referred to as operation 1 and operation 2. This new operation consists according to the invention in forcing home the thickenings located between the bearing positions, before the flattening, in the radial position of the crank-webs to be produced, this forcing home being effected, preferably by an amount which is so small that the under side of the thickening does not come quite into contact with the abutment, as indicated in FIGURE 7, or at any rate touches it only here and there. The extent by which the thickenings are forced home is therefore somewhat smaller than the distance a in FIGURES 1 and 2. Since the angle :1, before the flattening according to operation 1, is greater than the angle :11 in the case of a thickening flattened according to operation 2 (compare FIGURES 1 and 7), the fibers of metal bend at the point y during the forcing home without the point y being shifted downwards.

By the method according to the invention, therefore, according to the operation 1, flattening is not effected immediately, but the procedure will at first be according to FIGURE 7. In this FIGURE the thickening is still present in its original form before the flattening, the sides of the thickening forming the angle 1x1 with a radial plane of the shaft. The thickening is then shifted downwards by about the dimension a1, at being smaller than a. The upper surface 16, which, at the point where it leaves the holding bearing 2, forms the angle or}, thus becomes deformed to about the surface 16a, which, at the same point, now forms the angle a2 and the lower surface 17 becomes deformed to about the surface 17a, but does not yet touch the abutment 7.

The succeeding flattening, that is, the above mentioned operation 2, and the further treatment, may then be effected according to the aforementioned patent specifications, but it serves for the more reliable prevention of Wrinkles if the flattening of the thickenings, according to a further feature of the invention, when the thickening is enclosed by clamping bearings 34} and 31, is effected on the side opposite to the crank-pin to be produced, for then the flattening also effects a lengthening of the thickening in the direction of the contemplated crank-throw. During the flattening of the already eccentric thickening a filling piece 13, shown in FIGURES 8, 9 and 10, is placed in the die cavity 19 on the side 16a, which cavity moreover is of the same size on both sides of the shaft axis Zn. The material is thereby constrained to flow to the opposite side, that is to the left in FIGURES 8, 9 and 10. The dimension h in FIGURE 8 then increases to the magnitude hit in FIGURE 9, and the dimension a in FIGURE 7 becomes approximately zero. With this flattening the middle pressed-in surfaces marked 5 in FIGURE 1 for the tines Sb of the forked punch 8 are also produced. In the operation 3 which now follows, the step of forcing home, as illustrated in FIGURES 1 and 2, is no longer required. There now takes place only the complete filling 4 of the die according to FIGURES 3 and 4, and the pressing-Out of the crank-pin according to FIGURES 5 and 6. The resulting product in which the undesirable wrinkles at point X have been eliminated is shown in FIG. 11. I

The method according to the invention, when embodying both the improvements according to the invention, therefore embraces the following operation;

Operation 1: Pressing in the shaft bearings at the distance between bearing centres;

Operation in: Forcing home the pressed-in thickenings at the radial position of the crank-webs (FIGURE 7);

Operation 2: Rough pressing and pressing flat the eccentric thickenings with one-sided limitation of the die cavity (FIGURES 8 and 9);

Operation 3: Pressing out the crank-pins and crankwebs (FIGURES 3 to 6).

The operations 10, 2 and 3 thus share in the problem of displacing outwards to one side the material of the thickening, which is initially arranged concentrically around the axis of the shaft.

What we claim is:

A method of progressively forging a crank-shaft from a round shaft blank having spaced journals and an enlarged portion therebetween, said method comprising the steps of clamping said journals to prevent radial movement thereof, engaging said enlarged portion with a punch at one side and substantially midway between said journals and displacing said enlarged portion from said one side radially in the direction of a crank throw a distance less than the final length of a crank throw and less than a distance causing deformation at the point of juncture between said journals and said enlarged portion on said one side, removing said punch and engaging said one side with a fixed abutment, pressing said enlarged portion from opposite sides in a direction at right angles to the direction of a crank throw to displace said enlarged portion substantially only in the direction of a crank throw and provide flats on opposite sides of said enlarged portion and rough finish the crank webs of the crank throw, confining the axially opposite sides of said crank webs, engaging said one side and said flats midway between said journals with a forked punch having a thickness substantially equal to the length of a crank pin and displacing the material engaged by said forked punch into engagement with a fixed die to substantially form a crank pin with the excess displaced material flowing into said crank webs to finish the same.

References Cited in the file of this patent 

